[LEAPSECS] LEAPSECS Digest, Vol 45, Issue 1

Tony Finch dot at dotat.at
Fri Sep 3 05:18:15 EDT 2010

On 3 Sep 2010, at 05:50, Rob Seaman <seaman at noao.edu> wrote:

> I was referring to GMT broadly as "the astronomical timescale" and "for all practical purposes" "de facto the same as UTC".

My point is that if you are being precise this is nonsense. GMT in the historic sense of a solar timescale does not exist any more. Your systems cannot be synced to solar GMT in any precise sense. If you are syncing to a solar timescale it will have a different name. If you are syncing to what is now called "GMT" you are syncing to UTC because they are now in practice exact synonyms.

> I believe Tony is talking narrowly about the official "Greenwich Mean Time", more like http://bit.ly/cWcznJ, although it is pretty clear that the public remains very much "synced" to GMT, eg, http://bit.ly/aHWJYw

Yes well the discourse in the UK about Greenwich's place in the world is pretty delusional. Everyone basically ignores all developments since the mid 1950s: Airy's instrument still determines the prime meridian etc. It's a pity because the truth is a lot more interesting, and if we are to understand time and place properly it's instructive to know why the RGO was abolished and why WGS84 (and for that matter the ordnance survey grid) do not align with the Airy circle.

f.anthony.n.finch <dot at dotat.at> http://dotat.at/

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